The contents therein are incorporated herein by reference.
PCT patent application No. WO 00/02090 describes an elaborate procedure for preparing polymeric articles having a three-dimensionally periodic structure of a plurality of periodically occurring separate domains, with at least a first and a second domain each being topologically continuous and with the first domain comprising a polymeric species containing an inorganic species capable of forming a ceramic oxide. It is desirable to explore other approaches that could be more cost-effective.
Self-assembly of block copolymers have received extensive attention because of their fascinating phase behavior. Some of the studies have been reported by F. S. Bates in Science, 251, 898 (1991), and F. S. Bates and G. H. Fredrickson in Phys. Today, 32 (1990). Nanoscale microstructures from microphase separation can be obtained simply by chemically joining immiscible polymer chains together as block copolymers. Thermodynamically, the formed microstructure is the lowest Gibb free energy of morphology by balancing the enthalpic penalty and the entropic driving force of mixing, expressing as XN, the product of Flory-Huggins segmental interaction parameter X and the degree of polymerization N. One-, two-, and three-dimensional periodicities of self-assembled morphologies in bulk such as lamellar, cylindrical and gyroid microstructures have been identified with respect to various fractions of constituted blocks. These are reported in, e.g., F. S. Bates in Science, 251, 898 (1991); F. S. Bates and G. H. Fredrickson in Phys. Today, 32 (1990); S. Forster, A. K. Khandpur, J. Zhao, F. S. Bates, I. W. Hamley, A. J. Ryan, Bras W. Macromolecules 27, 6922 (1994); Vanessa Z. -H. Chan, J. Hoffman, V. Y. Lee, H. Iatrou, A. Avgeropoulos, N. Hadjichristidis, R. D. Miller, E. L. Thomas, Science 286, 1716 (1999); and F. S. Bates and G. H. Fredrickson, Annu. Rev. Phys. Chem. 41, 525 (1990). Defined textures can be easily tailored by molecular engineering of synthetic block copolymers that appears promising in the applications of nano-technologies. Examples of these reports can be found in M. Park, C. K. Harrison, P. M. Chaikin, R. A. Register, D. H. Adamson, Science 276, 1401 (1997); D. E. Fogg, L. H. Radzilowski, R. Balnski, R. R. Schrock, E. L. Thomas, Macromolecules 30, 417 (1997); Y. N. C. Chan, R. R. Schrock, R. E. Cohen, Chem. Mater. 4, 24 (1992); S. Fo{umlaut over ( )}rster, M. Antonietti, Adv. Mater. 10, 195 (1998); B. M. Discher, H. Bermudez, D. A. Hammer, D. E. Discher, Y. -Y. Won, F. S. Bates, J. Phys. Chem. B 106, 2848 (2002); A. -V. G. Ruzette, P. P. Soo, D. R. Sadoway, A. M. Mayes, J. Electrochem. Soc. 148, A537 (2001); N. Matsumi, K. Sugai, H. Ohno, Macromolecules 35, 5731 (2002); M. A. Hillmyer, P. M. Lipic, D. A. Hajduk, K. Almdal, F. S. Bates, J. Am. Chem. Soc. 119, 2749 (1997); P. M. Lipic, F. S. Bates, M. A. Hillmyer, J. Am. Chem. Soc. 120, 8963 (1998); J. M. Dean, P. M. Lipic, R. B. Grubbs, R. F. Cook, F. S. Bates, J. Polym. Sci., Part B: Polym. Phys. 39, 2996 (2001); and M. R. Buchmeiser, Angew. Chem., Int. Ed. 40, 3795 (2001).
Nature also employs the self-assembly of compounds as a tool for structuring substances. Biological architectures are formed by the interplay among steric, hydrophobic, hydgrogen-bonding, electrostatic interactions to form different levels of organization, i.e., different length-scales of morphologies. These morphologies are built from the smallest building blocks, e.g., amino acids, to achieve higher levels of organization. The self-assembly of synthetic supramolecules since its early days has been inspired by using these secondary interactions of biological matters, and has already created a large number of nanoscale architectures. Pursuing biological-like architectures by using synthetic systems has been, and still is the essential goals of many researchers in the fields of chemistry and physics. Among them, helical morphologies of different length-scales varying from helical chain conformations, helical aggregations to helical agglomerates are the most fundamental and interesting textures in biological systems. Discussions on this subject can be found in, e.g., H. Engelkamp, S. Middlebeek, R. J. M. Nolte, Science 284, 785 (1999); A. R. A. Palmans, J. A. J. M. Vekemans, E. E. Havinga, E. W. Meijer, Angew. Chem., Int. Ed. Engl. 36, 2648 (1997); T. Tachibana, H. Kambara, J. Am. Chem. Soc. 87, 3015 (1965); R. J. H. Hafkamp, B. P. A. Kokke, I. M. Danke, H. P. M. Geurts, A. E. Rowan, M. C. Feiters, R. J. M. Nolte, Chem. Commun., 545 (1997); K. Hanabusa, M. Yamada, M. Kimura, H. Shirai, Angew. Chem., Int. Ed. Engl. 35, 1949 (1996); M. De Loos, J. van Esch, I. Stokroos, R. M. Kellog, B. M. Feringa, J. Am. Chem. Soc. 119, 12675 (1997); and J. H. Van Esch, B. L. Feringa, Angew. Chem., Int. Ed. 39, 2263 (2000). Y. Okamoto,; K. Suzuki, K. Ohta, K. Hatada, H. Yuki, J. Am. Chem. Soc. 101, 4763 (1979) discussed the dissymmetric shapes of helical textures result in specific chemical and physical characters such as molecular recognition and optically active properties. S. I. Stupp, V. LeBonheur, K. Walker, L. S. Li, K. E. Huggins, M. Keser, and A. Amstutz, Science 276, 384 (1997) discussed desirable reasons for producing helical materials have been identified in the field of materials and life sciences.
The chirality of compounds has been referred to as one of the main origins for the formation of helical textures, and used as secondary interaction to assemble chiral molecules and macromolecules into larger helical structures. These have been discussed in, e.g., A. E. Rowan, R. J. M. Nolte, Angew. Chem., Int. Ed., 37, 63 (1998); and M. C. Feiters, R. J. M. Nolte, in Advances in Supramolecular Chemistry. Vol. 6. Chiral Self-assembled Structures of Biomolecules and Synthetic Analogues; G. W. Gokel, Ed.; JAI Press Inc.: Stamford, Conn.; Vol. 6, pp 41–156. Helical superstructures with a specific handedness have been obtained from buffer solutions of amphiphilic block copolymers containing charged helical blocks. As described by Nolte and co-workers, the chiral entity of constituted block aside from solvent, amphiphilicity and electrostatic effects plays important role for the formation of helical superstructures in solution. See, e.g., 29. J. J. L. M. Cornelissen, M. Fischer, N. A. J. M. Sommerdijk, R. J. M. Nolte, Science 280, 1427 (1998); N. A. M. M. Sommerdijk, S. J. Holder, R. C. Hiorns, R. G. Jones, R. J. M. Nolte, Macromolecules 33, 8289 (2000). Hillmyer and co-workers studied poly(styrene)-poly(D,L-lactide) (PS-PLA) and no helical morphologies were found. See, A. S. Zalusky, R. Olayo-Valles, C. J. Taylor, M. A. Hillmyer, J. Am. Chem. Soc. 123, 1519 (2001); and A. S. Zalusky, R. Olayo-Valles, J. H. Wolf, M. A. Hillmyer, J. Am. Chem. Soc. 124, 1276 (2002). It is well known that aliphatic polyesters such as poly(caprolactone) (PCL) and poly(lactide) (PLA) can be hydrolytically degraded owing to the unstable character of ester group. See, J. L. Kathleen, M. Edith, Biomaterials 19, 1973 (1998); A. Göpferich, Biomaterials 17, 103 (1996); and W. K. Lee, J. A. Gardella, Langmuir 16, 3401 (2000).